NRG1

- Phase 3 registrational trials evaluating petosemtamab in combination with pembrolizumab in 1L PD-L1+ r/m HNSCC and petosemtamab monotherapy in 2/3L r/m HNSCC enrolling; expected to be substantially enrolled by YE25 - Petosemtamab in combination with pembrolizumab in 1L PD-L1+ r/m HNSCC phase 2 trial ongoing with clinical data update planned for 1H25 - Petosemtamab evaluation in mCRC ongoing in combination with standard chemotherapy in 1L and 2L and monotherapy in 3L+; mCRC initial clinical data planned for 2H25 - Based on the Company’s current operating plan, existing cash, cash equivalents and marketable securities expected to fund Merus’ operations into 2028 UTRECHT, The Netherlands and CAMBRIDGE, Mass. , Feb. 27, 2025 (GLOBE NEWSWIRE) -- Merus N.V. (Nasdaq: MRUS) (Merus, the Company, we, or our), an oncology company developing innovative, full-length multispecific antibodies and antibody drug conjugates (Biclonics®, Triclonics® and ADClonics®), today announced financial results for the fourth quarter and full year and provided a business update. “We believe that petosemtamab’s receipt of two Breakthrough Therapy designations by the FDA – previously as monotherapy in the 2L+ treatment of r/m HNSCC and very recently, based on updated clinical efficacy, durability and safety of petosemtamab in combination with pembrolizumab in 1L PD-L1+ r/m HNSCC, indicates the potential for these treatment regimens to demonstrate substantial improvement over available therapies,” said Bill Lundberg, M.D., President, Chief Executive Officer of Merus. “We look forward to sharing the updated clinical data, including durability, for petosemtamab with pembrolizumab in 1L PD-L1+ r/m HNSCC, for the full phase 2 cohort, in the first half of 2025.” Petosemtamab (MCLA-158: EGFR x LGR5 Biclonics®): Solid TumorsLiGeR-HN1 phase 3 trial in 1L PD-L1+ r/m head and neck squamous cell carcinoma (HNSCC) and LiGeR-HN2 phase 3 trial in 2/3L r/m HNSCC enrolling – we expect both trials to be substantially enrolled by YE25; clinical update on phase 2 trial in combination with pembrolizumab in 1L PD-L1+ r/m HNSCC planned for 1H25; phase 2 trial in 1L, 2L and 3L+ metastatic colorectal cancer (mCRC) enrolling; mCRC initial clinical data planned for 2H25 In February 2025 , the U.S. Food and Drug Administration (FDA) granted Breakthrough Therapy designation (BTD) for petosemtamab in combination with pembrolizumab for the first-line treatment of adult patients with r/m PD-L1+ HNSCC with CPS ≥ 1. This designation was detailed in our press release, Petosemtamab granted Breakthrough Therapy designation by the U.S. FDA for 1L PD-L1 positive head and neck squamous cell carcinoma ( February 18 , 2025). In September 2024 , Merus announced the first patient was dosed in LiGeR-HN1, a phase 3 trial evaluating the efficacy and safety of petosemtamab in combination with pembrolizumab in 1L PD-L1+ r/m HNSCC compared to pembrolizumab. In this trial, patients will be randomized to petosemtamab plus pembrolizumab or pembrolizumab monotherapy. This was detailed in our press release, Merus Announces First Patient Dosed in LiGeR-HN1, a Phase 3 Trial Evaluating Petosemtamab in Combination with Pembrolizumab in 1L r/m HNSCC ( September 30 , 2024). Merus provided an interim clinical update on petosemtamab with pembrolizumab in 1L PD-L1+ r/m HNSCC at the American Society of Clinical Oncology ® (ASCO®) Annual Meeting 2024, demonstrating a 67% response rate among 24 evaluable patients. The oral presentation was detailed in our press release, Merus’ Petosemtamab in Combination with Pembrolizumab Interim Data Demonstrates Robust Response Rate and Favorable Safety Profile in 1L r/m HNSCC ( May 28, 2024 ). A clinical update on this cohort is planned for 1H25. In July 2024 , Merus announced the first patient was dosed in LiGeR-HN2, a phase 3 trial evaluating the efficacy and safety of petosemtamab in 2/3L HNSCC compared to standard of care. In this trial, patients will be randomized to petosemtamab monotherapy or investigator’s choice of single agent chemotherapy or cetuximab. This was detailed in our press release, Merus Announces First Patient Dosed in LiGeR-HN2, a Phase 3 Trial Evaluating Petosemtamab in 2/3L r/m HNSCC - Merus ( July 24 , 2024). Merus provided updated interim clinical data on petosemtamab in 2L+ r/m HNSCC at the European Society for Medical Oncology Asia Congress , demonstrating a 36% response rate among 75 evaluable patients. The oral presentation was detailed in our press release, Merus’ Petosemtamab Monotherapy Interim Data Continues to Demonstrate Clinically Meaningful Activity in 2L+ r/m HNSCC ( Dec. 7 , 2024). In May 2024 , the FDA granted BTD for petosemtamab for the treatment of patients with recurrent or metastatic HNSCC whose disease has progressed following treatment with platinum based chemotherapy and an anti-programmed cell death receptor-1 (PD-1) or anti-programmed death ligand 1 (PD-L1) antibody. This designation was detailed in our press release, Petosemtamab granted Breakthrough Therapy Designation by the U.S. FDA ( May 13 , 2024). Merus believes a randomized registration trial in HNSCC with an overall response rate endpoint could potentially support accelerated approval and the overall survival results from the same study could potentially verify its clinical benefit to support regular approval. In the third quarter 2024, Merus announced the first patient was dosed in a phase 2 trial evaluating petosemtamab in combination with standard chemotherapy in 2L mCRC. This was detailed in our press release, Merus Announces First Patient Dosed in Phase 2 Trial of Petosemtamab in 2L CRC ( July 8, 2024 ). In the fourth quarter 2024, Merus announced the first patient was dosed in a phase 2 trial evaluating petosemtamab monotherapy in heavily pretreated (3L+) mCRC. This was detailed in our press release, Merus announces First Patient Dosed in Phase 2 Trial of Petosemtamab in 3L+ mCRC ( Dec. 16, 2024 ). In January 2025 , the first patient was dosed in a phase 2 trial evaluating petosemtamab in combination with standard chemotherapy in 1L mCRC. We expect to provide initial clinical data for petosemtamab in mCRC in 2H25. BIZENGRI® (zenocutuzumab-zbco: HER2 x HER3 Biclonics®)Approved by FDA for adults with pancreatic adenocarcinoma or non–small cell lung cancer (NSCLC) that are advanced unresectable or metastatic and harbor a neuregulin 1 (NRG1) gene fusion who have disease progression on or after prior systemic therapy In December 2024 , the FDA approved BIZENGRI® (zenocutuzumab-zbco), the first and only treatment indicated for adults with pancreatic adenocarcinoma or NSCLC that are advanced unresectable or metastatic and harbor a NRG1 gene fusion who have disease progression on or after prior systemic therapy. These indications are approved under accelerated approval based on overall response rate (ORR) and duration of response (DOR). Continued approval for these indications may be contingent upon verification and description of clinical benefit in a confirmatory trial(s). BIZENGRI® has a Boxed WARNING for Embryo-Fetal Toxicity and warnings for infusion-related reactions (IRRs), hypersensitivity and anaphylactic reactions, interstitial lung disease (ILD)/pneumonitis, and left ventriculardysfunction.1 See Important Safety Information below. This was detailed in our press release, Merus Announces FDA Approval of BIZENGRI® (zenocutuzumab-zbco) for NRG1+ Pancreatic Adenocarcinoma and NRG1+ Non–Small Cell Lung Cancer (NSCLC) Based on Safety and Efficacy Data From the eNRGy Study ( December 4 , 2024). Merus has exclusively licensed to Partner Therapeutics the right to commercialize BIZENGRI® for the treatment of NRG1+ cancer in the U.S. This was detailed in our press release, Merus and Partner Therapeutics Announce License Agreement for the U.S. Commercialization of Zenocutuzumab in NRG1 Fusion-Positive Cancer ( December 2 , 2024). MCLA-129 (EGFR x c-MET Biclonics®): Solid Tumors Investigation of MCLA-129 is ongoing in METex14 NSCLC; phase 2 trial in combination with chemotherapy in 2L+ EGFR mutant (EGFRm) NSCLC enrolling In the third quarter 2024, Merus announced the first patients were dosed in the phase 2 trial evaluating MCLA-129 in combination with chemotherapy in 2L+ EGFRm NSCLC, with a cohort receiving MCLA-129 and paclitaxel and carboplatin, and another cohort receiving MCLA-129 and docetaxel. We remain interested in partnering MCLA-129 to sufficiently resource the development of MCLA-129 and the potential benefit it may have for patients. MCLA-129 is subject to a collaboration and license agreement with Betta Pharmaceuticals Co. Ltd. (Betta), which permits Betta to develop MCLA-129, and potentially commercialize exclusively in China, while Merus retains global rights outside of China. Collaborations Incyte CorporationSince 2017, Merus has been working with Incyte Corporation (Incyte) under a global collaboration and license agreement focused on the research, discovery and development of bispecific antibodies utilizing Merus’ proprietary Biclonics® technology platform. For each program under the collaboration, Merus receives reimbursement for research activities and is eligible to receive potential development, regulatory and commercial milestones and sales royalties for any products, if approved. Eli Lilly and CompanyIn January 2021, Merus and Eli Lilly and Company (Lilly) announced a research collaboration and exclusive license agreement to develop up to three CD3-engaging T-cell re-directing bispecific antibody therapies utilizing Merus’ Biclonics® platform and proprietary CD3 panel along with the scientific and rational drug design expertise of Lilly. The collaboration is progressing well with three programs advancing through preclinical development. Gilead SciencesIn March 2024, Merus and Gilead Sciences announced a collaboration to discover novel antibody based trispecific T-cell engagers using Merus’ patented Triclonics® platform. Under the terms of the agreement, Merus will lead early-stage research activities for two programs, with an option to pursue a third. Gilead will have the right to exclusively license programs developed under the collaboration after the completion of select research activities. If Gilead exercises its option to license any such program from the collaboration, Gilead will be responsible for additional research, development and commercialization activities for such program. Merus received an equity investment by Gilead of $25 million in Merus common shares and an upfront payment of $56 million. Ono PharmaceuticalIn 2018, the Company granted Ono Pharmaceutical Co., Ltd. (Ono) an exclusive, worldwide, royalty-bearing license, with the right to sublicense, research, test, make, use and market a limited number of bispecific antibody candidates based on Merus’ Biclonics® technology platform directed to an undisclosed target combination. During the third quarter of 2024, Merus achieved and received a milestone payment based on the filing of an Investigational New Drug (IND) application in Japan. BiohavenIn January 2025 , Merus and Biohaven announced a research collaboration and license agreement to co-develop three novel bispecific antibody drug conjugates (ADCs), leveraging Merus’ leading Biclonics® technology platform, and Biohaven’s next-generation ADC conjugation and payload platform technologies. Under the terms of the agreement, Biohaven is responsible for the preclinical ADC generation of three Merus bispecific antibodies under mutually agreed research plans. The agreement includes two Merus bispecific programs generated using the Biclonics® platform, and one program under preclinical research by Merus. Each program is subject to mutual agreement for advancement to further development, with the parties then sharing subsequent external development costs and commercialization, if advanced. Cash Runway, existing cash, cash equivalents and marketable securities expected to fund Merus’ operations into 2028 As of December 31, 2024, Merus had $724.0 million cash, cash equivalents and marketable securities. Based on the Company’s current operating plan, the existing cash, cash equivalents and marketable securities are expected to fund Merus’ operations into 2028. Full Year 2024 Financial Results Collaboration revenue for the year ended December 31, 2024 decreased $7.8 million as compared to the year ended December 31, 2023 , primarily as a result of decreases in Lilly revenue of $8.4 million and Incyte revenue of $6.4 million , offset by increases in Gilead revenue of $4.8 million , and Other revenue of $2.2 million . The decrease in Lilly revenue is primarily the result of decreases in upfront payment amortization of $4.8 million and reimbursement revenue of $3.6 million . The decrease in Incyte revenue is primarily the result of decreases in milestone revenue of $5.0 million and reimbursement revenue of $1.4 million . Gilead revenue increased due to the start of the collaboration agreement in 2024 which resulted in an increase in upfront payment amortization of $4.8 million . The increase in Other revenue is primarily the result of increases in milestone revenue of $2.1 million . Research and development expense for the year ended December 31, 2024 increased $84.7 million as compared to the year ended December 31, 2023 , primarily as a result of increases in external clinical services and drug manufacturing costs of $66.6 million , which primarily includes costs to advance our petosemtamab program and costs to fulfill our obligations under our collaboration agreements related to our programs, increases in personnel related expenses including share-based compensation of $11.8 million due to an increase in employee headcount and an increase in share price, consultancy expenses of $5.5 million , facilities expenses and other related expenses of $0.7 million , and consumables expenses of $0.2 million , offset by decreases in depreciation and amortization of $0.1 million . General and administrative expense for the year ended December 31, 2024 increased $23.0 million as compared to the year ended December 31, 2023 , primarily as a result of increases in personnel related expenses including share-based compensation of $12.6 million due to an increase in employee headcount and an increase in share price, consultancy expenses of $6.8 million , legal expenses of $1.8 million , facilities and depreciation expense of $1.2 million , and intellectual property and licenses expenses of $0.7 million . Other income, net consists of interest earned on our cash and cash equivalents held on account, accretion of investment earnings and net foreign exchange gains or losses on our foreign denominated cash, cash equivalents and marketable securities, and payables and receivables. Please see full Prescribing Information, including Boxed WARNING, at BIZENGRI.com/pi. Reference: 1. BIZENGRI. Prescribing information. Merus N.V. ; 2024. About Merus N.V. Merus is an oncology company developing innovative full-length human bispecific and trispecific antibody therapeutics, referred to as Multiclonics®. Multiclonics® are manufactured using industry standard processes and have been observed in preclinical and clinical studies to have several of the same features of conventional human monoclonal antibodies, such as long half-life and low immunogenicity. For additional information, please visit Merus’ website, and LinkedIn. Forward-Looking Statements This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. All statements contained in this press release that do not relate to matters of historical fact should be considered forward-looking statements, including without limitation, statements regarding the content and timing of clinical trials, data readouts and clinical, regulatory, strategy and development updates for our product candidates; our ongoing LiGeR-HN1, LiGeR-HN2 and phase 2 mCRC trials for petosemtamab, our planned update in the 1H 2025 on the phase 2 cohort of 1L r/m PD-L1+ HNSCC; our planned initial clinical data update on the phase 2 investigation of petosemtamab in mCRC; our belief that petosemtamab’s receipt of two BTDs by the FDA – previously as monotherapy in the 2L+ treatment of r/m HNSCC and very recently, based on updated clinical efficacy, durability and safety of petosemtamab in combination with pembrolizumab in 1L PD-L1+ r/m HNSCC, indicates the potential for these treatment regimens to demonstrate substantial improvement over available therapies; the potential benefits of BTD for petosemtamab’s development, if any; our looking forward to sharing the updated clinical data, including durability, for petosemtamab with pembrolizumab in 1L PD-L1+ r/m HNSCC, for the full phase 2 cohort, in the first half of 2025; our expectation that the LiGeR-HN1 and LiGeR-HN2 studies will be substantially enrolled by year-end; our belief that a randomized registration trial in HNSCC with an overall response rate endpoint could potentially support accelerated approval and the overall survival results from the same study could potentially verify its clinical benefit to support regular approval; statements regarding the sufficiency of our cash, cash equivalents and marketable securities, and expectation that it will fund the Company into 2028; the continued investigation of MCLA-129 in monotherapy in Met ex14 NSCLC, and enrolling of patients in the investigation of MCLA-129 in combination with chemotherapy in 2L+ EGFRm NSCLC; our interest in partnering MCLA-129 to sufficiently resource the development of MCLA-129 and the potential benefit it may have for patients; the benefits of the license from Merus to PTx for the commercialization of Bizengri® in the US for NRG1+ cancer, collaborations between Incyte and Merus, Lilly and Merus, Gilead and Merus, Biohaven and Merus, and license agreement between Ono and Merus; and the potential of those licenses and collaborations for future value generation, including whether and when Merus will receive any future payments, including milestones or royalties, and the amounts of such payments; whether any programs under the collaboration will be successful; and our collaboration and license agreement with Betta, which permits Betta to develop MCLA-129 and potentially commercialize exclusively in China, while Merus retains full ex-China rights, including any future clinical development by Betta of MCLA-129. These forward-looking statements are based on management’s current expectations. These statements are neither promises nor guarantees, but involve known and unknown risks, uncertainties and other important factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements, including, but not limited to, the following: our need for additional funding, which may not be available and which may require us to restrict our operations or require us to relinquish rights to our technologies or antibody candidates; potential delays in regulatory approval, which would impact our ability to commercialize our product candidates and affect our ability to generate revenue; the lengthy and expensive process of clinical drug development, which has an uncertain outcome; the unpredictable nature of our early stage development efforts for marketable drugs; potential delays in enrollment of patients, which could affect the receipt of necessary regulatory approvals; our reliance on third parties to conduct our clinical trials and the potential for those third parties to not perform satisfactorily; impacts of the volatility in the global economy, including global instability, including the ongoing conflicts in Europe and the Middle East; we may not identify suitable Biclonics® or bispecific antibody candidates under our collaborations or our collaborators may fail to perform adequately under our collaborations; our reliance on third parties to manufacture our product candidates, which may delay, prevent or impair our development and commercialization efforts; protection of our proprietary technology; our patents may be found invalid, unenforceable, circumvented by competitors and our patent applications may be found not to comply with the rules and regulations of patentability; we may fail to prevail in potential lawsuits for infringement of third-party intellectual property; and our registered or unregistered trademarks or trade names may be challenged, infringed, circumvented or declared generic or determined to be infringing on other marks. These and other important factors discussed under the caption “Risk Factors” in our Quarterly Report on Form 10-K for the period ended December 31, 2024, filed with the Securities and Exchange Commission, or SEC, on February 27, 2025, and our other reports filed with the SEC, could cause actual results to differ materially from those indicated by the forward-looking statements made in this press release. Any such forward-looking statements represent management’s estimates as of the date of this press release. While we may elect to update such forward-looking statements at some point in the future, we disclaim any obligation to do so, even if subsequent events cause our views to change, except as required under applicable law. These forward-looking statements should not be relied upon as representing our views as of any date subsequent to the date of this press release. Bizengri®, Multiclonics®, Biclonics®, Triclonics® and ADClonics® are registered trademarks of Merus N.V. Source: Merus N.V.

BIZENGRI® is the first and only FDA-approved therapy specifically for patients with advanced unresectable or metastatic pancreatic adenocarcinoma or non-small cell lung cancer (NSCLC) who harbor NRG1 gene fusions1 NRG1 gene fusions are best detected by tissue-based RNA next generation sequencing (NGS)3 LEXINGTON, Mass., Feb. 5, 2025 /PRNewswire/ -- Partner Therapeutics, Inc. (PTx), a private, fully-integrated biotechnology company announced today that the New England Journal of Medicine (NEJM) published results of the 204-patient, global, multicenter, single-arm, Phase 2 clinical trial of zenocutuzumab-zbco (BIZENGRI®) (eNRGy trial; NCT02912949).2 The eNRGy trial evaluated overall response rate to zenocutuzumab-zbco in patients with NRG1 gene fusions across multiple tumor types. Responses by tumor type and safety data are detailed in the NEJM manuscript. Continue Reading "Zenocutuzumab helps fill an important need for patients with advanced pancreatic cancer and NSCLC with NRG1 gene fusions," said Alison Schram M.D., an attending medical oncologist in the Early Drug Development Service at Memorial Sloan Kettering Cancer Center, a principal investigator for the eNRGy trial, and lead author on the NEJM manuscript. "The overall response rate and durability of responses we observed in the eNRGy trial are noteworthy. I strongly encourage my colleagues to obtain tissue-based RNA NGS to identify NRG1 rearrangements and other oncogenic gene alterations, particularly in otherwise driver-negative tumors, as fusions often are missed by DNA-based NGS techniques." New England Journal of Medicine Publishes eNRGy Trial Evaluating Zenocutuzumab-zbco (BIZENGRI®) in NRG1+ cancer Post this "The eNRGy study highlights that NRG1 fusions are an actionable therapeutic target and the importance of developing biomarker driven therapies like zenocutuzumab," said Debasish Roychowdhury, MD, Chief Technology Officer at PTx. "We are deeply grateful to the Merus team that designed, researched and developed zenocutuzumab, the eNRGy trial investigators, and the dedicated study participants who helped advance this important research." A subset of data from the eNRGy trial reported in the NEJM publication supported the recent FDA approval of BIZENGRI in adult patients with pancreatic adenocarcinoma or NSCLC that are advanced unresectable or metastatic and harbor a neuregulin 1 (NRG1) gene fusion who have disease progression on or after prior systemic therapy. These indications are approved under accelerated approval based on overall response rate (ORR) and duration of response (DOR). Continued approval for these indications may be contingent upon verification and description of clinical benefit in a confirmatory trial(s). BIZENGRI® has a Boxed WARNING for Embryo-Fetal Toxicity and warnings for infusion-related reactions (IRRs), hypersensitivity and anaphylactic reactions, interstitial lung disease (ILD)/pneumonitis, and left ventricular dysfunction.1 See Important Safety Information below. Under an agreement with Merus, PTx has exclusive rights to develop, manufacture, and commercialize zenocutuzumab-zbco for the treatment of NRG1+ cancer in the U.S. and provide the product on a named-patient basis for this use outside of the U.S. pending future regulatory developments. The companies are working to provide BIZENGRI for commercial distribution as quickly as possible. About NRG1 Gene Fusions NRG1 fusions are unique cancer drivers that create oncogenic chimeric ligands rather than the more widely described chimeric receptors (NTRK, RET, ROS1, ALK, and FGFR fusions). The chimeric ligands bind to HER3, triggering HER2/HER3 heterodimerization and activating downstream signaling pathways that cause cancer cells to grow and proliferate. Zenocutuzumab-zbco is a bispecific antibody that blocks HER2/HER3 dimerization and NRG1 fusion interactions with HER3, resulting in the suppression of these pathways. About BIZENGRI ( zenocutuzumab-zbco) INDICATIONS BIZENGRI is indicated for the treatment of adults with advanced unresectable or metastatic non-small cell lung cancer (NSCLC) harboring a neuregulin 1 (NRG1) gene fusion with disease progression on or after prior systemic therapy. BIZENGRI is indicated for the treatment of adults with advanced unresectable or metastatic pancreatic adenocarcinoma harboring a neuregulin 1 (NRG1) gene fusion with disease progression on or after prior systemic therapy. These indications are approved under accelerated approval based on overall response rate and duration of response. Continued approval for these indications may be contingent upon verification and description of clinical benefit in a confirmatory trial(s). Important Safety Information BOXED WARNING: EMBRYO-FETAL TOXICITY Embryo-Fetal Toxicity: Exposure to BIZENGRI during pregnancy can cause embryo-fetal harm. Advise patients of this risk and the need for effective contraception. WARNINGS AND PRECUATIONS Infusion-Related Reactions/Hypersensitivity/Anaphylactic Reactions BIZENGRI can cause serious and life-threatening infusion-related reactions (IRRs), hypersensitivity and anaphylactic reactions. Signs and symptoms of IRR may include chills, nausea, fever, and cough. In the eNRGy study, 13% of patients experienced IRRs, all were Grade 1 or 2; 91% occurred during the first infusion. Administer BIZENGRI in a setting with emergency resuscitation equipment and staff who are trained to monitor for IRRs and to administer emergency medications. Monitor patients closely for signs and symptoms of infusion reactions during infusion and for at least 1 hour following completion of first BIZENGRI infusion and as clinically indicated. Interrupt BIZENGRI infusion in patients with ≤ Grade 3 IRRs and administer symptomatic treatment as needed. Resume infusion at a reduced rate after resolution of symptoms. Immediately stop the infusion and permanently discontinue BIZENGRI for Grade 4 or life-threatening IRR or hypersensitivity/anaphylaxis reactions. Interstitial Lung Disease/Pneumonitis BIZENGRI can cause serious and life-threatening interstitial lung disease (ILD)/pneumonitis. In the eNRGy study, ILD/pneumonitis occurred in 2 (1.1%) patients treated with BIZENGRI. Grade 2 ILD/pneumonitis (Grade 2) resulting in permanent discontinuation of BIZENGRI occurred in 1 (0.6%) patient. Monitor for new or worsening pulmonary symptoms indicative of ILD/pneumonitis (e.g., dyspnea, cough, fever). Immediately withhold BIZENGRI in patients with suspected ILD/pneumonitis and administer corticosteroids as clinically indicated. Permanently discontinue BIZENGRI if ILD/pneumonitis ≥ Grade 2 is confirmed. Left Ventricular Dysfunction BIZENGRI can cause left ventricular dysfunction. Left ventricular ejection fraction (LVEF) decrease has been observed with anti-HER2 therapies, including BIZENGRI. Treatment with BIZENGRI has not been studied in patients with a history of clinically significant cardiac disease or LVEF less than 50% prior to initiation of treatment. In the eNRGy study, Grade 2 LVEF decrease (40%-50%; 10 - 19% drop from baseline) occurred in 2% of evaluable patients. Cardiac failure without LVEF decrease occurred in 1.7% of patients, including 1 (0.6%) fatal event. Before initiating BIZENGRI, evaluate LVEF and monitor at regular intervals during treatment as clinically indicated. For LVEF of less than 45% or less than 50% with absolute decrease from baseline of 10% or greater which is confirmed, or in patients with symptomatic congestive heart failure (CHF), permanently discontinue BIZENGRI. Embryo-Fetal Toxicity Based on its mechanism of action, BIZENGRI can cause fetal harm when administered to a pregnant woman. No animal reproduction studies were conducted with BIZENGRI. In postmarketing reports, use of a HER2-directed antibody during pregnancy resulted in cases of oligohydramnios manifesting as fatal pulmonary hypoplasia, skeletal abnormalities, and neonatal death. In animal models, studies have demonstrated that inhibition of HER2 and/or HER3 results in impaired embryo-fetal development, including effects on cardiac, vascular and neuronal development, and embryolethality. Advise patients of the potential risk to a fetus. Verify the pregnancy status of females of reproductive potential prior to the initiation of BIZENGRI. Advise females of reproductive potential to use effective contraception during treatment with BIZENGRI and for 2 months after the last dose. ADVERSE REACTIONS NRG1 Gene Fusion Positive Unresectable or Metastatic NSCLC Serious adverse reactions occurred in 25% of patients with NRG1 Gene Fusion Positive NSCLC who received BIZENGRI. Serious adverse reactions in ≥ 2% of patients included pneumonia (n=4) dyspnea and fatigue (n=2 each). Fatal adverse reactions occurred in 3 (3%) patients and included respiratory failure (n=2), and cardiac failure (n=1). Permanent discontinuation of BIZENGRI due to an adverse reaction occurred in 3% of patients. Adverse reactions resulting in permanent discontinuation of BIZENGRI included dyspnea, pneumonitis and sepsis (n=1 each). In patients with NRG1 Gene Fusion Positive NSCLC who received BIZENGRI, the most common (>20%) Adverse Reactions, including laboratory abnormalities, were decreased hemoglobin (35%), increased alanine aminotransferase (30%), decreased magnesium (28%), increased alkaline phosphatase (27), decreased phosphate (26%) diarrhea (25%), musculoskeletal pain (23%), increased gamma-glutamyl transpeptidase (23%), increased aspartate aminotransferase (22%), and decreased potassium (21%). NRG1 Gene Fusion Positive Unresectable or Metastatic Pancreatic Adenocarcinoma Serious adverse reactions occurred in 23% of patients with NRG1 Gene Fusion Positive Pancreatic Adenocarcinoma who received BIZENGRI. There were 2 fatal adverse reactions, one due to COVID-19 and one due to respiratory failure. In patients with NRG1 Gene Fusion Positive Pancreatic Adenocarcinoma who received BIZENGRI the most common (≥20%) adverse reactions, including laboratory abnormalities, were increased alanine aminotransferase (51%), diarrhea (36%), increased aspartate aminotransferase (31%), increased bilirubin (31%), decreased phosphate (31%), increased alkaline phosphatase (28%), decreased sodium (28%) musculoskeletal pain (28%), decreased albumin (26%), decreased potassium (26%), decreased platelets (26%), decreased magnesium (24%), increased gamma-glutamyl transpeptidase (23%), decreased hemoglobin (23%),vomiting (23%), nausea (23%), decreased leukocytes (21%), and fatigue (21%). Please see full Prescribing Information, including Boxed Warning About Partner Therapeutics Partner Therapeutics, Inc. (PTx), an integrated biotechnology company, focuses on development and commercialization of therapeutics to improve health outcomes in cancer and other serious diseases. The company believes in delivering products and supporting medical teams with the purpose of achieving superior outcomes for patients and their families. Visit the PTx website and LinkedIn. References: BIZENGRI® (zenocutuzumab-zbco) injection [package insert]. Available at: Schram AM, Goto K, Kim DW, et al. Efficacy of Zenocutuzumab in NRG1 Fusion–Positive Cancer. N Engl J Med. 2025;392:566-76. doi: 10.1056/NEJMoa2405008 Drilon A, Duruisseaux M, Han JY, et al. Clinicopathologic Features and Response to Therapy of NRG1 Fusion-Driven Lung Cancers: The eNRGy1 Global Multicenter Registry. J Clin Oncol. 2021;39(25):2791-2802. doi:10.1200/JCO.20.03307 BIZENGRI® is a registered trademark of Merus N.V. PARTNER THERAPEUTICS® is a registered trademark owned by Partner Therapeutics, Inc. ©2025 Partner Therapeutics, All rights reserved. Investor and Media Inquiries: Partner Therapeutics Media Relations 781-786-2405 [email protected] SOURCE Partner Therapeutics, Inc. WANT YOUR COMPANY'S NEWS FEATURED ON PRNEWSWIRE.COM? 440k+ Newsrooms & Influencers 9k+ Digital Media Outlets 270k+ Journalists Opted In GET STARTED

UTRECHT, The Netherlands and CAMBRIDGE, Mass., Feb. 05, 2025 (GLOBE NEWSWIRE) -- Merus N.V. (Nasdaq: MRUS) (Merus, the Company, we, or our), a clinical-stage oncology company developing innovative, full-length multispecific antibodies (Biclonics® and Triclonics®), today announced that the New England Journal of Medicine (NEJM) published results of the registrational phase 2 eNRGy trial for Bizengri® (zenocutuzumab), the first and only treatment indicated for adults with pancreatic adenocarcinoma or non–small cell lung cancer (NSCLC) that are advanced unresectable or metastatic and harbor a neuregulin 1 (NRG1) gene fusion who have disease progression on or after prior systemic therapy. “This manuscript provides comprehensive data on the safety and efficacy of Bizengri® and demonstrates the meaningful results observed in the eNRGy trial,” said Bill Lundberg, M.D., President, Chief Executive Officer of Merus. “We continue to make significant progress across our clinical pipeline of important and new cancer therapeutic candidates, all from our own Biclonics® antibody technologies.” NRG1 fusions are unique cancer drivers that create oncogenic chimeric ligands rather than the more widely described chimeric receptors (TRK, RET, ROS1, ALK, and FGFR fusions). This is the first reported prospective clinical trial targeting cancers with this rare genomic alteration, a population enriched for cancer types with limited effective treatment options.1, 2, 3 The publication reviews the results of 204 patients with 12 tumor types enrolled and treated on the eNRGy study, concluding “Zenocutuzumab demonstrated durable efficacy in patients with advanced NRG1+ cancer, notably NSCLC and pancreatic adenocarcinoma, with a favorable safety profile.” “This medicine fills an important need among patients with NRG1 fusion pancreatic adenocarcinoma and lung cancer who have not previously had targeted treatment options,” said Alison Schram M.D., an attending medical oncologist in the Early Drug Development Service at Memorial Sloan Kettering Cancer Center, a principal investigator for the eNRGy trial, and lead author on the NEJM manuscript. In December, Merus announced it had entered into an agreement with Partner Therapeutics, Inc. (PTx), a private, fully-integrated biotechnology company with a focus in hematology and oncology, in which Merus has exclusively licensed to PTx the right to commercialize zenocutuzumab (Zeno, tradename Bizengri®) for the treatment of NRG1 fusion-positive (NRG1+) cancer in the United States (U.S.). Indications: BIZENGRI® (zenocutuzumab-zbco) is indicated for adults with pancreatic adenocarcinoma or non–small cell lung cancer (NSCLC) that are advanced unresectable or metastatic and harbor a neuregulin 1 (NRG1) gene fusion who have disease progression on or after prior systemic therapy. These indications are approved under accelerated approval based on overall response rate (ORR) and duration of response (DOR). Continued approval for these indications may be contingent upon verification and description of clinical benefit in a confirmatory trial(s). IMPORTANT SAFETY INFORMATION BOXED WARNING: EMBRYO-FETAL TOXICITY Embryo-Fetal Toxicity: Exposure to BIZENGRI® during pregnancy can cause embryo-fetal harm. Advise patients of this risk and the need for effective contraception. WARNINGS AND PRECAUTIONS Infusion-Related Reactions/Hypersensitivity/Anaphylactic Reactions BIZENGRI® can cause serious and life-threatening infusion-related reactions (IRRs), hypersensitivity and anaphylactic reactions. Signs and symptoms of IRR may include chills, nausea, fever, and cough. In the eNRGy study, 13% of patients experienced IRRs, all were Grade 1 or 2; 91% occurred during the first infusion. Administer BIZENGRI® in a setting with emergency resuscitation equipment and staff who are trained to monitor for IRRs and to administer emergency medications. Monitor patients closely for signs and symptoms of infusion reactions during infusion and for at least 1 hour following completion of first BIZENGRI® infusion and as clinically indicated. Interrupt BIZENGRI® infusion in patients with ≤ Grade 3 IRRs and administer symptomatic treatment as needed. Resume infusion at a reduced rate after resolution of symptoms. Immediately stop the infusion and permanently discontinue BIZENGRI® for Grade 4 or life-threatening IRR or hypersensitivity/anaphylaxis reactions. Interstitial Lung Disease/Pneumonitis BIZENGRI® can cause serious and life-threatening interstitial lung disease (ILD)/pneumonitis. In the eNRGy study, ILD/pneumonitis occurred in 2 (1.1%) patients treated with BIZENGRI®. Grade 2 ILD/pneumonitis (Grade 2) resulting in permanent discontinuation of BIZENGRI® occurred in 1 (0.6%) patient. Monitor for new or worsening pulmonary symptoms indicative of ILD/pneumonitis (e.g., dyspnea, cough, fever). Immediately withhold BIZENGRI® in patients with suspected ILD/pneumonitis and administer corticosteroids as clinically indicated. Permanently discontinue BIZENGRI® if ILD/pneumonitis ≥ Grade 2 is confirmed. Left Ventricular Dysfunction BIZENGRI® can cause left ventricular dysfunction. Left ventricular ejection fraction (LVEF) decrease has been observed with anti-HER2 therapies, including BIZENGRI®. Treatment with BIZENGRI® has not been studied in patients with a history of clinically significant cardiac disease or LVEF less than 50% prior to initiation of treatment. In the eNRGy study, Grade 2 LVEF decrease (40%-50%; 10 - 19% drop from baseline) occurred in 2% of evaluable patients. Cardiac failure without LVEF decrease occurred in 1.7% of patients, including 1 (0.6%) fatal event. Before initiating BIZENGRI®, evaluate LVEF and monitor at regular intervals during treatment as clinically indicated. For LVEF of less than 45% or less than 50% with absolute decrease from baseline of 10% or greater which is confirmed, or in patients with symptomatic congestive heart failure (CHF), permanently discontinue BIZENGRI®. Embryo-Fetal Toxicity Based on its mechanism of action, BIZENGRI® can cause fetal harm when administered to a pregnant woman. No animal reproduction studies were conducted with BIZENGRI®. In postmarketing reports, use of a HER2-directed antibody during pregnancy resulted in cases of oligohydramnios manifesting as fatal pulmonary hypoplasia, skeletal abnormalities, and neonatal death. In animal models, studies have demonstrated that inhibition of HER2 and/or HER3 results in impaired embryo-fetal development, including effects on cardiac, vascular and neuronal development, and embryolethality. Advise patients of the potential risk to a fetus. Verify the pregnancy status of females of reproductive potential prior to the initiation of BIZENGRI®. Advise females of reproductive potential to use effective contraception during treatment with BIZENGRI® and for 2 months after the last dose. ADVERSE REACTIONS NRG1 Gene Fusion Positive Unresectable or Metastatic Pancreatic Adenocarcinoma Serious adverse reactions occurred in 23% of patients with NRG1 Gene Fusion Positive Pancreatic Adenocarcinoma who received BIZENGRI®. There were 2 fatal adverse reactions, one due to COVID-19 and one due to respiratory failure. In patients with NRG1 Gene Fusion Positive Pancreatic Adenocarcinoma who received BIZENGRI® the most common (≥20%) adverse reactions, including laboratory abnormalities, were increased alanine aminotransferase (51%), diarrhea (36%), increased aspartate aminotransferase (31%), increased bilirubin (31%), decreased phosphate (31%), increased alkaline phosphatase (28%), decreased sodium (28%) musculoskeletal pain (28%), decreased albumin (26%), decreased potassium (26%), decreased platelets (26%), decreased magnesium (24%), increased gamma-glutamyl transpeptidase (23%), decreased hemoglobin (23%), vomiting (23%), nausea (23%), decreased leukocytes (21%), and fatigue (21%). NRG1 Gene Fusion Positive Unresectable or Metastatic NSCLC Serious adverse reactions occurred in 25% of patients with NRG1 Gene Fusion Positive NSCLC who received BIZENGRI®. Serious adverse reactions in ≥ 2% of patients included pneumonia (n=4) dyspnea and fatigue (n=2 each). Fatal adverse reactions occurred in 3 (3%) patients and included respiratory failure (n=2), and cardiac failure (n=1). Permanent discontinuation of BIZENGRI® due to an adverse reaction occurred in 3% of patients. Adverse reactions resulting in permanent discontinuation of BIZENGRI® included dyspnea, pneumonitis and sepsis (n=1 each). In patients with NRG1 Gene Fusion Positive NSCLC who received BIZENGRI®, the most common (>20%) Adverse Reactions, including laboratory abnormalities, were decreased hemoglobin (35%), increased alanine aminotransferase (30%), decreased magnesium (28%), increased alkaline phosphatase (27%), decreased phosphate (26%) diarrhea (25%), musculoskeletal pain (23%), increased gamma-glutamyl transpeptidase (23%), increased aspartate aminotransferase (22%), and decreased potassium (21%). Please see full Prescribing Information, including Boxed WARNING, at BIZENGRI.com/pi. About BIZENGRI® BIZENGRI® is a bispecific antibody that binds to the extracellular domains of HER2 and HER3 expressed on the surface of cells, including tumor cells, inhibiting HER2:HER3 dimerization and preventing NRG1 binding to HER3. BIZENGRI® decreased cell proliferation and signaling through the phosphoinositide 3-kinase-AKT-mammalian target of rapamycin pathway. In addition, BIZENGRI® mediates antibody-dependent cellular cytotoxicity. BIZENGRI® showed antitumor activity in mouse models of NRG1+ lung and pancreatic cancers.4 About the eNRGy Trial The eNRGy trial (Clinicaltrials.gov NCT02912949) is a multicenter, open-label clinical trial that includes patients with advanced unresectable or metastatic NRG1+ pancreatic adenocarcinoma or NRG1+ NSCLC who have disease progression on or after prior systemic therapy. There were 30 patients in the NRG1+ pancreatic adenocarcinoma group and 64 patients in the NRG1+ NSCLC group. The main outcome measures were ORR and DOR, as determined by BICR according to Response Evaluation Criteria in Solid Tumors (RECIST) v1.1.4 In the NRG1+ pancreatic adenocarcinoma group, the median age was 49 years (range, 21-72 years); 43% were female; 87% were White, 7% were Asian, and 3.3% were Black or African American. All patients had an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1, and all patients had metastatic disease. Patients received a median of 2 prior systemic therapies (range, 0-5); 97% had prior systemic therapy with prior chemotherapy.4 In the NRG1+ NSCLC group, the median age was 64 years (range, 32-86 years); 64% were female, 33% were White, 56% were Asian, and 3.4% were Black or African American. ECOG performance status was 0 or 1 in 97% of patients or 2 in 3% of patients, and 98% of patients had metastatic disease. Patients received a median of 2 prior systemic therapies (range, 1-6).4 Forward-Looking Statements This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. All statements contained in this press release that do not relate to matters of historical fact should be considered forward-looking statements, including without limitation, benefits of a license between PTx and Merus; whether and when Merus will receive any future payment under the license agreement, including milestones or royalties, and the amounts of such payments; our progress across our clinical pipeline of important and new cancer therapeutic candidates, all from our own Biclonics® antibody technologies; the belief that this medicine fills an important need among patients with NRG1 fusion pancreatic adenocarcinoma and lung cancer who have not previously had targeted treatment options. These forward-looking statements are based on management’s current expectations. These statements are neither promises nor guarantees, but involve known and unknown risks, uncertainties and other important factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements, including, but not limited to, the following: our need for additional funding, which may not be available and which may require us to restrict our operations or require us to relinquish rights to our technologies or antibody candidates; potential delays in regulatory approval, which would impact our ability to commercialize our product candidates and affect our ability to generate revenue; the lengthy and expensive process of clinical drug development, which has an uncertain outcome; the unpredictable nature of our early stage development efforts for marketable drugs; potential delays in enrollment of patients, which could affect the receipt of necessary regulatory approvals; our reliance on third parties to conduct our clinical trials and the potential for those third parties to not perform satisfactorily; impacts of the volatility in the global economy, including global instability, including the ongoing conflicts in Europe and the Middle East; we may not identify suitable Biclonics® or bispecific antibody candidates under our collaborations or our collaborators may fail to perform adequately under our collaborations; our reliance on third parties to manufacture our product candidates, which may delay, prevent or impair our development and commercialization efforts; protection of our proprietary technology; our patents may be found invalid, unenforceable, circumvented by competitors and our patent applications may be found not to comply with the rules and regulations of patentability; we may fail to prevail in potential lawsuits for infringement of third-party intellectual property; and our registered or unregistered trademarks or trade names may be challenged, infringed, circumvented or declared generic or determined to be infringing on other marks. These and other important factors discussed under the caption “Risk Factors” in our Quarterly Report on Form 10-Q for the period ended September 30, 2024, filed with the Securities and Exchange Commission, or SEC, on October 31, 2024, and our other reports filed with the SEC, could cause actual results to differ materially from those indicated by the forward-looking statements made in this press release. Any such forward-looking statements represent management’s estimates as of the date of this press release. While we may elect to update such forward-looking statements at some point in the future, we disclaim any obligation to do so, even if subsequent events cause our views to change, except as required under applicable law. These forward-looking statements should not be relied upon as representing our views as of any date subsequent to the date of this press release. References: 1Chang JC, Offin M, Falcon C, et al. Comprehensive molecular and clinicopathologic analysis of 200 pulmonary invasive mucinous adenocarcinomas identifies distinct characteristics of molecular subtypes. Clin Cancer Res 2021;27:4066-76. 2Drilon A, Duruisseaux M, Han JY, et al. Clinicopathologic features and response to therapy of NRG1 fusion-driven lung cancers: the eNRGy1 global multicenter registry. J Clin Oncol 2021;39:2791-802. 3Garon EB, Ciuleanu TE, Arrieta O, et al. Ramucirumab plus docetaxel versus placebo plus docetaxel for second-line treatment of stage IV non-small-cell lung cancer after disease progression on platinum-based therapy (REVEL): a multicentre, double-blind, randomised phase 3 trial. Lancet 2014;384:665-73. 4BIZENGRI. Prescribing information. Merus N.V.; 2024. About Merus Merus is a clinical stage oncology company developing innovative full-length human bispecific and trispecific antibody therapeutics, referred to as Multiclonics®. Multiclonics® are manufactured using industry standard processes and have been observed in preclinical and clinical studies to have several of the same features of conventional human monoclonal antibodies, such as long half-life and low immunogenicity. For additional information, please visit Merus’ website, and LinkedIn. Multiclonics®, Biclonics®, Triclonics®, and Bizengri® are registered trademarks of Merus N.V. Source: Merus N.V.